of akron



C. L. WALTON. TIRE MOLD. APPLICATION men APR-16, l92l.

Patented May 31,192].

N n W w & W M a UNITED STATES PATENT ore-10E,

CHARLES L. WALTON. OF AKRON. OHIO. ASSIGNOR TO KELLY-SPRINGFIELD TIRE COMPANY OF AKRON. OHIO. A CORPORATION OF NEW JERSEY.

TIRE-MOLD.

Application filed April 16, 1921.

meats in the art of molding artielesof manu- Jfa'rture. such as re raslngs. formed 111 Specification of Letters Patent.

1 whole, or in part, of plastic material and has for itsprintapal ob eet the provision of ;certai n air vents, or traps. in a mold. so

locatedwith respect to the tread configuration=oavities that the material being molded willflow freely into and completely till the mold without resulting defects due to trapping-ah; or gases generated during the molding process.

To the attainment of these and other useful objects herein appearing this invention consists in the new and useful combination of features more fully hereinafter described. illustrated in the drawings and. specifically claimed.

Figure l is.a cross sectional view of a moldemhodying my invention. particularly illustrating a green. or uncured, tire casing mounted on a core and the whole inserted within a separable mold of annular form preparatory to'closing the mold under heat and pressure toefi'eet the molding operation. The mold is arbitrarily broken away to illustrate the tread cavity.

Fig. 2 is a perspective view of a tire fully molded in the type of mold invented, particularly showing theresult of theair venting as related to the specific design of' mold cavity to which the features claimed apply.

Referring specifically to the drawings:-

This invention refers specifically to a mold made in halves 3. having cavities 4 therein adapted to impart a complementary configuration 11. such as shown. to the tread portion of a pneumatic tire casing 7. The.

igh-standiug configurations nceessitatecorrespondingly deep mold (a1-vities. and as the transverse contour of the tread surface. as ultimately molded. is substantially flat. and therefore the natural path of How of the material and escape of gases toward the central annular vent of the mold restricted. it has become necessary to provide auxiliary Patented May 31, 1921. Serial no. 481.895.

air vents 5 in the outer limits cavities. M.

In the particular operation of molding. for which this mold. with its cavities of of the mold specified formation and peculiar secondary V airvents 1s applicable. it istomary to sub ect the mold shells to hvr rimhzcqclosing pressures. ranglng occaslonally aho umdrcd pounds per square inch; the pressure hemg exerted concurrently with the application of vulcaniziug heat applied for several hours.

. As the combined heatand )ressure are applied tothe article heing molded a gradual softening or plasticity' is imparted to the material. thus inducing conformit' thereof with the interstices of the mold. The cavities for overflow and of gases. hoth central 6 and auxiliaryfi, are so proportioned as to nicely accommodate the predetermined surplus of stock that must escape when the mold adjusts itself to the completely closed position. Due to the great internal pressure. thefsmall amounts of gas that are trapped within the several auxiliary air vents 5 do not interfere with.

at least. a partial filling upof the vents by the overflowing material. The tra ped gas will he eo'mpwssed within the top ofthe auailiar vents. In Fi 2 will be noted the upstanding overflow fill 10 caused bythe flow throu h the central rent 6 prior to the complete than of the shells. also the elon gated points 0 overflow 9 which represent that part of the material seeking relief within the air vents 5. These rejections are, of course. finally removed mm a tire within the tire 7 which preferably is originally formed thereon and removed therefrom only upon the completion of the moldingprocess. I i 1 It will be noted that the central overflow 6 is designed to accommodate the bulk of the excess material which. during the closing operation. is extruded within the constantly narrowing circumferential line of cleavage between the shells. Should the overflow he particularly copiousa'nmllar receases 12 are provided into whichjhq material may expand. attention hein invited to the fact that as soon-as the mo] s start closing the offset registers on either shell, ad

casing. The annular core 8 is shown incased 1 sure upon the shells.

compressed therein by the encroaching flow,

each vent becomes a miniature air cylinder in which the extruded plug of overflow is the piston, balanced by a pressure equal to that interiorly exerted upon the mate-rial be ing molded by the enormous closing pres- The practical use of this back pressure in each air vent is that complete equalization of the mass of mate rial being molded will result: that it there should be an undue mass of material concentrated at one point of the uncured casing and a proportional deficit at another it has been found that as the air vents fill up adjacent the excess during the progress of molding the resilient action of the air Vlinder will react to expel a portion of the column or plug as the mass becomes snlliciently plastic to tend to flow toward the unfilled portions. This equalizing flow is slow but positive. as may be appreciated in view of the time element in conjunction with the heat and pressure present.

It will be understood that the mold. of which a section only is illustrated. is of an nular form; also that the particular cavity configuration. shown in cross section in the. mold, is complementary to the molded tread design configurationll and that the design is repeated throughout the. internal peripheral surface of the tread portion of the mold.

-While a particular form of pneumatic casing is shown, and with it a ccrtam type of core, it will be understood that the disclosure is by Way of illustration only. and that my mold can be adapted to the manufacture of any type-of tire on any type of core; or on an expanding core or air bag.

Having thus described my invention. what Iclaim as new therein and desire to secure by Letters Patent is: f

1. A mold comprising separable scctions.

each section having a design cut therein inintaglio; a register adapted to scrvc as an tvorflow for a portion of the excess of an article molded therein: and air traps in said molds at approximately the ontcr limits of cachelement of the design.

2. A mold comprising separable counterpart sections. each section having a design cut therein in intaglio: n co-acting register point at the top of the mold adaptcd to serve as an overflow for a ortion of the excess of an article molded therein; and air traps 1 ,aeopss in each mold scction'at approximately the outer limits of each separate element of the design. said traps being in open couununication with the inside of the mold but sealed at their outer ends. I

3. A mold comprising separable counter-/ part sections. each adapted to register with the other to confine the overflow. from the excess of an article therein being molded within the cavity therein formed: a design within the mold sect ions executed in intaglio. said design having a substantially llat transverse t'ace contour: sealed air traps located at approximately the outer limits of each separate clcmcnt oi the design and adapted to receive a portion of the excess flow of material in resilient compression therein. 0

l. mold comprising separable counterpart sections: an overllowand register point circumi'ercntial ot' the molds at approximately lhcir median plane of incident z'a design in iutaglio witlnn the molds. said deig'l] being of cruciform pattern in each. mold section: and air traps at aproximately the outer limits of each element of each cruciform pattern. said traps bein in open (t)lllllllllllttlllllll with the interior ol the'mold and adapted to receive a part of the excess of the material within the mold.

5. mold comprising separable counterpart sections of annular form; 'co-acting register and overflow portions on each section: a design in iutaglio within the molds, said dcr 'ign being of cruciform pattern and ap n'oximatcly llat in transverse section; sealed air traps located at approximately the high points at tpe outer limits of indiridual clcuu-nts of the pattern, said tra. 5 being pro iortionedto accommodate, in t e aggregate. a part 0 the excess of the material bciug molded} during the progress of the overllow of the same under pressure and subjected to heat. V

(i. A mold comprising separable counterpart sections of annular form; co-acting register and ovcu'llow portions on eafi cctiou; a design infintaglio within the mo t said design being of cruciform pattern and approximately that in transverse section; sealed air traps fat the outer corners of each clement of the lintaglio pattern, said traps haying capaciti s adapted to at least accommodate the'cxrcss of material remaining within the mod al'tcr theoverllowcavity between the m lld halves has been filled.

7. In a dcvie of the character described, the combinati m of a rigid core having thereon an art cle to'he molded consisting of material ada ted .to become plastic under heat, and mo d sections in halves adapted to incase the article and the core, said mold having an overflow cavity along one edge of its registering plane and a cruciform pattern therein in in aglio, and air traps located at 1,sso,o ee i to receive the overflow of the material but sealed at their outer ends to form compression chambers adapted to equalize the distic under heat, means for interior trihuting the lastic materlal during the progress of mo ding.

8. In a device of the character described, the combination of an article to be molded formed of material adapted to become plassupporting the article, said article havlng an excess amount of material to more than "iill the mold cavities constituting the. design to be impressed thereon; and mold sections having a normal overflow of capacity less than the excess of the material and a plurality of sealed air traps located adjacent the outer limits of each element of the intaglio design in the mold, the aggregate capacity of such air traps being regulated to accommodate the excess of the plastic material under elastic pressure.

'9. In a mold device, thei combination of means for interiorly supporting an article to be molded; an article to be molded comprising an excess of material above that require to fill the design cavities of the mold, said material being adapted to become plastic under heat; and a mold surrounding the article and its support, said mold having an annular overflow aperture adapted to accommodate less than the excess of the material when the mold is closed 'andseconda sealed overflow cavities lobated within the intaglio design, said secondary overflow cavities being adapted to resiliently receive a part of the excess of the material during the-process of closingthe mold under pressure whereby the plastic material will be equalized throughout the mold.

In testimony whereof I ailix my signature.

' CHARLES L. WALTON. 

